The last of the five: The elusive "tantalum(III) bromide", a perovskite-related salt, [{Ta6}Br12]Br 3[TaBr6]0.86

Abstract

The system Ta/Br contains, according to a phase diagram deterrnination of 1965, five compounds. The crystal structures of TaBr5, TaBr 4 as well as of Ta6Br15 and Ta 6Br14 are known. The elusive "TaBr3" was now obtained as single crystals from the reduction of TaBr5 at the wall of the tantalum reaction container in the presence of a NaBr or RbBr flux. Its structure is that of a stuffed derivative of the structure of Ta 6Br15. As this is related to the ReO3-type of structure, "TaBr3" is related to the perovsMte-type of structure, in accord with the formulation [(Ta6}Br 12]Br3[TaBr6]0.862(13, = [Ti]O3[Ca], with an under-occupation of the cuboctahedral site. With the composition TaBr2.94 it represents the lower end of a homogeneity range TaBr3-x once reported. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.